On Wed, Jan 6, 2010 at 3:35 AM, Ian Lynagh
Hi all,
Currently, when GHC reports an error it only gives a source position, not a source span. For example, with this module:
main = print (f (const 'x' 'x') 'y') f xs y = xs ++ [y]
you get an error starting:
u.hs:1:18: Couldn't match expected type `[a]' against inferred type `Char'
There's a (probably little-known) flag -ferror-spans with which you get this error instead:
u.hs:1:18-30: Couldn't match expected type `[a]' against inferred type `Char'
i.e. rather than just giving the start column number 18, it gives you the span 18-30 (the "const 'x' 'x'").
Would you find the extra information useful, or just noise? i.e. should we show error spans by default?
Thanks Ian
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I certainly wouldn't find it distracting, and I think it could be quite useful in many cases. I vote for turning it on by default. Alex